1. Field of the Invention
The invention relates to the field of controllers, particularly controllers for interfacing between a digital computer and a magnetic recorder such as a floppy disc or other memories.
2. Prior Art
Numerous controllers are commercially available for interfacing between digital computers and magnetic disc recorders such as the commonly employed floppy disc recorders. These discs include a plurality of endless, concentric tracks used for storing digital data. The controller typically accepts data in parallel form from the computer and provides the data in serial form to the recorder. Serialized data from the recorder is converted to parallel form for the computer. Controllers perform other functions such as track selection and synchronization.
Commercially available controllers, particularly those for floppy disc recorders, are generally complex and expensive. Because of their cost, they do not lend themselves to the consumer field (e.g., hobby and home uses) or small business use. As will be seen, with the present invention a relatively simple, inexpensive controller is described which is suitable for consumer and small business applications. However, the principles employed in the described controller are applicable to larger, more elaborate systems.
Ofter disc controllers provide track selection signals to the recorder. These signals control a stepping motor which drives the read-write head to the desired track. If the motor is stepped from track-to-track, considerable time is lost in selecting non-adjacent tracks. In the prior art, complex means are used to allow the stepping motor to accelerate and decelerate to and from higher speeds when selecting tracks which are separated from one another by some distance. With the present invention, a computed velocity profile is easily implemented, thus allowing rapid selection of non-adjacent tracks.
When a track is selected, synchronization between the controller/computer and the data recorded on the track is necessary. In some cases, permanent markers, such as holes, are included with each track to provide a fixed reference point. In "soft-sectored" discs, permanent markers are not used. These discs provide wider flexibility since the user is able to format the disc to a particular application. Somewhat intricate hardware is used to provide synchronization with these soft-sectored discs. A method is described in this application which provides rapid synchronization for soft-sectored discs.